Caspian Isinglass, a versatile and sustainable biocatalyst for domino synthesis of…
General procedure for synthesis of spirooxindoles 4a–4w
and spiroacenaphthylene derivatives 6a–6e catalyzed by
IG
A mixture of isatin derivatives (1a–1d, 1 mmol) or
acenaphthoquinone (5, 1 mmol), methylene nitriles (2a,
2b, 1 mmol), 1,3-dicarbonyl (3, 1 mmol), and 5 mg IG in
3 cm3 H2O was stirred at 60 °C for the mentioned time
shown in tables. Rapid conversion of reagents can be
clearly confirmed by reaction color change. The progress of
the reaction was monitored by TLC using EtOAc/n-hexane
(1:3) as an eluent. Upon completion, the reaction mixture
was allowed to cool to room temperature and the precip-
itate was obtained from the reaction mixture by filtration.
The product 4a was dissolved in DMSO and the catalyst
was separated by simple filtration. Pure products were
afforded by evaporation of the solvent under reduced
pressure.
Fig. 4 SEM image of powdered IG
with EtOH and EtOAc, respectively, dried at room tem-
perature and reused in the model reaction. Although some
decrease in catalytic activity was observed after four runs
(Fig. 2), the catalyst could be used at least four times
without significant loss of activity.
Acknowledgments The authors gratefully acknowledge the support
of the Research Council of Iran University of Science and Technol-
ogy, Tehran, Iran.
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The fish bladders were first washed in hot water to
remove extraneous material. The bladders were then cut
and soaked in ethanol and stirred for 24 h, collected by
filtration, washed with water, and dried at room tem-
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123